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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
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    <title>Document</title>
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<body>
    <script>
        // while (条件表达式) {
        //     语句...
        // }
        var num = 10;
        while (num > 0) {
            console.log(num);
            num--;
        }
        // 10 9 8 7 6 5 4 3 2 1
    </script>
</body>

</html>